This invention relates to the monitoring and control of electrical circuits and in particular to means for controlling the three-phase power supply to systems requiring overload and undercurrent protection.
Many electrical systems require the immediate detection of electrical faults and the subsequent disconnecting of system power until such faults are corrected. For instance, airborne radar systems must be protected in this manner in order to avoid damage to radar equipment, smoke in the aircraft cockpit, and other damage of the type that frequently results from power distribution malfunctions. Protection circuits used in airborne and other applications should be lightweight and reliable. It is also desirable that they have adjustable threshold values and that they be easily resettable. In addition, many applications require that the protection circuit include means for preventing false triggering resulting from system noise and short duration faults. Conventional state-of-the-art protection devices in general fail to meet all of the above criteria. The present invention is directed toward providing a protective circuit that will meet all of the above and other objectives.